1. Field of the Invention
The embodiment disclosed herein relates to an optical writing control device, an image forming apparatus, and a method of controlling an optical writing device, and especially relates to a configuration of a pattern drawn to correct the drawing position of an image.
2. Description of the Related Art
In recent years, there has been a trend to promote the digitization of information. Image processing apparatuses such as printers and facsimiles that are used to output digitized information and scanners used to digitize documents have become indispensable apparatuses. In many cases, such an image processing apparatus is configured as a multifunction peripheral that can be used as a printer, a facsimile, a scanner, and a copying machine by including an image capture function, an image forming function, a communication function, and the like.
Among such image processing apparatuses, an electrophotographic image forming apparatus is widely used as an image forming apparatus used to output digitized documents. The electrophotographic image forming apparatus exposes a photosensitive element to form an electrostatic latent image, develops the electrostatic latent image with developer such as toner to form a toner image, and transfer the toner image onto a piece of paper to output the paper.
Such an electrophotographic image forming apparatus synchronizes the timing to expose the photosensitive element and draw an electrostatic latent image with the timing to convey the paper and accordingly makes adjustments so as to form an image within a proper area on the paper. Moreover, a tandem image forming apparatus that forms a color image with a plurality of photosensitive elements adjusts exposure timing at the photosensitive element of each color so as to accurately overlap images developed at the photosensitive elements of the respective colors. Hereinafter, these adjustment processes are collectively referred to as the misalignment correction.
Specific methods for realizing such misalignment correction as have been described above include a mechanical adjustment method for adjusting an arrangement relationship between a light source to expose the photosensitive element and the photosensitive element, and a method by image processing that adjusts an image to be output in accordance with misalignment to eventually form the image at a suitable position. In a case of the method by image processing, it is configured such that a pattern for correction is drawn and read and accordingly a correction is mage based on a difference between the timing determined in terms of design and the timing at which the pattern is actually read and an image is formed at a desired position.
Moreover, a technology for improving the accuracy of reading by a sensor that reads the pattern for correction is proposed for the method by image processing (see, for example, Japanese Laid-open Patent Publication No. 2004-069767). In Japanese Laid-open Patent Publication No. 2004-069767, after a correction is made based on a pattern for correction drawn with a margin for an area of reading by a reading sensor, in other words, a pattern for correction drawn larger to avoid any trouble with reading even if misalignment is occurring, a pattern for correction drawn in a size corresponding to the area of reading by the reading sensor is drawn to perform the correction process again. Consequently, in the second correction process to be executed, the influence of diffuse reflection light from an extra drawn part can be excluded and the highly accurate correction process becomes possible.
In a case of the technology disclosed in Japanese Laid-open Patent Publication No. 2004-069767, if misalignment is caused between the time when a correction is made based on the pattern for correction drawn with a margin for the area of reading by the reading sensor and the time when a correction is made based on the pattern for correction drawn in the size corresponding to the area of reading by the reading sensor, the pattern drawn in a state where the margin for the area of reading is small is not suitably read. As a consequence, a correction is not accurately made based on the pattern for correction drawn in the size corresponding to the area of reading by the reading sensor, and the accuracy of the operation of the apparatus is impaired.
In view of the above circumstances, there is a need to balance a reduction in the amount of toner consumption related to the drawing of the pattern for correction with the accuracy of the operation of the apparatus.